We compare the observed X-ray luminosity emitted from pulsars with that calculated from various theoretical models and find that the X-ray emission from six pulsars is much stronger than that predicted by theoretical models. We suggest that these pulsars with unusually intense X-ray emission could also be γ-ray emitters. Electrons/positrons are accelerated in the outer magnetospheric gap and lose most of their energy via curvature radiation (primary photons), which will be converted to secondary e ± pairs outside the gap in collision with the secondary X-rays. A simple synchrotron self-Compton model is then used to calculate the X-ray and γ-ray emission from the secondary e ± pairs. This model only contains a single free parameter, which characterizes the size of the acceleration region and can be estimated by comparison with that of the Crab pulsar. Our model results are consistent with the observed data and upper limits of γ-ray emission and phase separation between pulses. Other implications for future observations are also discussed in the text.

We compare the observed X-ray luminosity emitted from pulsars with that calculated from various theoretical models and find that the X-ray emission from six pulsars is much stronger than that predicted by theoretical models. We suggest that these pulsars with unusually intense X-ray emission could also be γ-ray emitters. Electrons/positrons are accelerated in the outer magnetospheric gap and lose most of their energy via curvature radiation (primary photons), which will be converted to secondary e ± pairs outside the gap in collision with the secondary X-rays. A simple synchrotron self-Compton model is then used to calculate the X-ray and γ-ray emission from the secondary e ± pairs. This model only contains a single free parameter, which characterizes the size of the acceleration region and can be estimated by comparison with that of the Crab pulsar. Our model results are consistent with the observed data and upper limits of γ-ray emission and phase separation between pulses. Other implications for future observations are also discussed in the text.

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Institute of Physics Publishing Ltd. The Journal's web site is located at http://iopscience.iop.org/2041-8205